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-rw-r--r--llvm/lib/CodeGen/LiveIntervals.cpp30
1 files changed, 30 insertions, 0 deletions
diff --git a/llvm/lib/CodeGen/LiveIntervals.cpp b/llvm/lib/CodeGen/LiveIntervals.cpp
index 79fdba7e062..13fe77e4866 100644
--- a/llvm/lib/CodeGen/LiveIntervals.cpp
+++ b/llvm/lib/CodeGen/LiveIntervals.cpp
@@ -1291,6 +1291,36 @@ private:
if (OldIdxIn != E && SlotIndex::isEarlierInstr(NewIdx, OldIdxIn->end))
OldIdxIn->end = NewIdx.getRegSlot();
}
+ } else if (OldIdxIn != E
+ && SlotIndex::isEarlierInstr(NewIdxOut->start, NewIdx)
+ && SlotIndex::isEarlierInstr(NewIdx, NewIdxOut->end)) {
+ // OldIdxVNI is a dead def that has been moved into the middle of
+ // another value in LR. That can happen when LR is a whole register,
+ // but the dead def is a write to a subreg that is dead at NewIdx.
+ // The dead def may have been moved across other values
+ // in LR, so move OldIdxOut up to NewIdxOut. Slide [NewIdxOut;OldIdxOut)
+ // down one position.
+ // |- X0/NewIdxOut -| ... |- Xn-1 -| |- Xn/OldIdxOut -| |- next - |
+ // => |- X0/NewIdxOut -| |- X0 -| ... |- Xn-1 -| |- next -|
+ std::copy_backward(NewIdxOut, OldIdxOut, std::next(OldIdxOut));
+ // Modify the segment at NewIdxOut and the following segment to meet at
+ // the point of the dead def, with the following segment getting
+ // OldIdxVNI as its value number.
+ *NewIdxOut = LiveRange::Segment(
+ NewIdxOut->start, NewIdxDef.getRegSlot(), NewIdxOut->valno);
+ *(NewIdxOut + 1) = LiveRange::Segment(
+ NewIdxDef.getRegSlot(), (NewIdxOut + 1)->end, OldIdxVNI);
+ OldIdxVNI->def = NewIdxDef;
+ // Modify subsequent segments to be defined by the moved def OldIdxVNI.
+ for (auto Idx = NewIdxOut + 2; Idx <= OldIdxOut; ++Idx)
+ Idx->valno = OldIdxVNI;
+ // Aggressively remove all dead flags from the former dead definition.
+ // Kill/dead flags shouldn't be used while live intervals exist; they
+ // will be reinserted by VirtRegRewriter.
+ if (MachineInstr *KillMI = LIS.getInstructionFromIndex(NewIdx))
+ for (MIBundleOperands MO(*KillMI); MO.isValid(); ++MO)
+ if (MO->isReg() && !MO->isUse())
+ MO->setIsDead(false);
} else {
// OldIdxVNI is a dead def. It may have been moved across other values
// in LR, so move OldIdxOut up to NewIdxOut. Slide [NewIdxOut;OldIdxOut)
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